This invention relates to the field of selecting one or more sets of experimental tires of one construction. More particularly, the present invention relates to a method for selecting one or more sets of tires from a larger group of experimentally built tires so that the performance of the matched set(s) will behave as randomly chosen sets from uniform production runs.
According to the prior art, during the development of a new tire construction for a specific car, a number of different tire experimental constructions are typically produced. Each of these constructions has different variations of the same construction parameters. Typically about five to forty tires are produced for each of the experimental tire constructions. Then, these tires are subjected to a number of tests in the laboratory to measure various operating parameters such as for example lateral and radial force variation, weight, and visual appearance. From each of the different constructions of experimental tires, a set of four, ideally closely matched tires are selected for evaluation purposes. The tires, which are to be representative of each of the different constructions of experimental tires, are typically selected by tire serial numbers in the order of construction. Among the constructed tires, some tires do not always meet original equipment (OE) limits on specifications, such as for example, force variation, weight or visual defects. The result of selecting tires based on preset specifications is a set of four tires for each construction with serial numbers, such as for example, 2,3,4,6 or 8,9,10,11, assigned to each of the tires in each experimental group of tires. These sets of tires for each construction are then road tested by expert drivers to assess their performance based on subjective criteria. Using various criteria, including the laboratory results and the subjective handling characteristics, the suitability of each construction is evaluated as to whether it meets the desired operating performance. Due to the variations inherent in each of the experimental tires, there is always a possibility that one set of four experimental tires will produce enhanced handling characteristics while a different set of the same construction of experimental tires will have poorer handling characteristics. Therefore, this method of selection has been found to sometimes result in sets of tires of the same experimental construction which give erratic results as compared to other sets of tires of the same experimental construction. The latter method can be particularly erratic where only on,set per experimental construction is tested because the non-repeatability of the sets is hidden. Another deficiency in this method of tire selection is that rebuilds or production models of apparently good constructions are frequently unable to repeat the results of the selected group.
It is an object of the present invention to provide a method of testing experimental tire sets of one construction to obviate the problems and limitations of the prior art methods.
It is another object of the present invention to increase the repeatability of performance of a set of experimental tires of one construction by selecting a specific combination of tires to form a set of four tires from a larger group of experimental tires for a vehicle.
Another object of the invention is to select a set of experimental tires of one construction based on criteria including plysteer, conicity, load sensitivity, residual forces on each axle and the position each individual tire is mounted on the rim, and to the vehicle.
Still another object of the invention is to select a set of experimental tires of one construction with a tire prediction software program based on criteria including plysteer, conicity, load sensitivity, residual forces on each axle and the position each individual tire is mounted on the rim, and to the vehicle.
Accordingly, there is provided a method for selecting a set of tires from a group of experimental tires. The method comprising the steps of: a) determining the average lateral force for each tire of a group of experimental tires for both a first tire deflection and for a second tire deflection; b) determining the stability of the front and rear axles with respect to each other and selecting groupings of pairs of tires for mounting to the front and rear axles so that the residual force on the rear axle (RESR) at the first tire deflection is equal to or a predetermined amount greater than the residual force on the front axle (RESF) at the first tire deflection; c) determining the load sensitivity using the RESF and the RESR, both at the second tire deflection, and selecting groupings of pairs of tires the second tire deflection for mounting to the front and rear axles so that the absolute value of the RESR at the second tire deflection is equal to or a predetermined amount greater than the absolute value of the RESF at the second tire deflection and that the absolute value of the RESF at the second tire deflection is equal or greater than the absolute value of the RESF at the first tire deflection; d) determining the preload on the front and rear axles based on the RESF and the RESR, both at the first tire deflection, and selecting groupings of pairs of tires for mounting to the front and rear axles so that the RESF and RESR, both at the first tire deflection, are greater than a predetermined maximum value or less than a predetermined minimum value; and e) selecting a set of four tires for front and rear axles which meet the criteria set forth in steps b, c, and d.